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Denaturing Gradient Gel Electrophoresis or DGGE is used to separate and detect DNA molecules that differ by as little as a single nucleotide. The electrophoretic separation is based on the melting properties of the double-stranded DNA molecule. The two complimentary strands of DNA separate (melt) under conditions of increased temperature or under the influence of denaturing chemicals. An increase in the temperature and/or concentration of chemical denaturant around a DNA molecule will cause it to melt along its length in discrete segments or regions, called melting domains. Melting domains vary in length between about 25 up to several hundred bases, and each melts cooperatively at a distinct temperature called a Tm. The Tm of a melting domain is highly dependent on its nucleotide sequence and even a single-base substitution is sufficient to alter the Tm of a domain.